Waves Chapter 11

Wave Properties Newton’s Laws govern the motion of waves All waves transmit energy Water, sound, light

Wave types Mechanical waves Transverse wave water, sound, waves that travel down a spring Require a medium (water, air, ropes, springs) Transverse wave A type of mechanical wave Wave vibrates perpendicular to the direction of the wave motion

Wave Types Longitudinal Surface Wave Particles move parallel to the direction of the wave motion Sound, fluids Surface Wave Particles both parallel and perpendicular to the direction of the motion Characteristics of long. And transverse

Measuring a wave Drawing Frequency Speed

Assignment Page 387 (1-4)

Boundaries

Superposition of Waves 2 waves in the same place in the medium at the same time Pulse down meeting a reflected pulse Each affects the medium independently 2 or more waves can combine to form a new wave Principle of superposition

Interference If the two waves are in opposite directions, they can cancel or form a new wave of less or greater amplitude The result of the superposition of 2 or more waves is interference Wave interference can be either constructive or destructive

Destructive Interference The superposition of waves with equal but opposite amplitudes causes destructive In. When 2 pulses with = but opp. Amplitudes meet, the displacement of the medium at each point in the overlap region is reduced (↑ & ↓) When the pulses meet (node) the displacement is zero. The waves pass through each other unchanged and resume their original form as they continue to move

Constructive Interference Occurs when the wave displacements are in the same direction (↑ & ↑) The resulting wave has an amplitude larger than any of the individual waves The point where the 2 waves meet that has the largest displacement is the antinode

If the pulses have opposite and unequal amplitudes, the resultant pulse at the overlap is the algebraic sum of the two pulses Page 394

Waves in >1 dimension Mechanical waves move in 1D, Surface water waves move in 2D, Sound and electromagnetic waves move in 3D A ripple tank can be used to show the properties of 2D waves The wave pulse travels toward a barrier that reflects the wave (incident wave moves upward and the reflected wave moves to the right)

Diagram Ray diagrams model the movement of waves Rays show the direction of the wave (drawn at right angles to the crests) The direction of the barrier is shown with a line drawn at a right angle Called the normal θi = θr (law of reflection)

Diffraction Drawing Reflection, refraction, and diffraction will be used in optics